Thank you very much!!!Yes that was the problem...I remember this problem whit displacement but I did not think also for refraction!!!Thank also for the notice of the latest version 
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by the way I follow the all tutorials for glass but I can not get the glass that I see to other and that I want!There is too distorcion of image behind and strange color. I post two images with settings of my rendering,the illumination's settings are default vray. 
There is also the glass that I wish.
